Superman Punch, Jump Punch, Skip Punch, whatever you want to all it. Yes, when it works is sweet. Looks cool and alot of potential power there. However as so many have already said, this technique can leave you wide open. The attacker is lunging foreward, which by nature puts him off balance, and is wide open for counter attack. One of the main reasons we don't see missed attempts end badly for the attacker and why we don't see it countered often is due to poor defensive techniques.
Even when setup with a low leg kick or fake knee or other such technique, the SMP is very often telegraphed, (becuse of the time it takes to close the distance) and the defender sees it coming. (I'm talking in general and not like the Savant SMP, from the video previously posted in this thread. That was well setup and lightning fast) Ok so if the opponent sees it coming, why isn't it countered more. Lets look at what we see the defender do most often. They see it coming and imediately cover up and start moving backwards. Both of these things, at least in my opinion are very bad defensive techniques. First off, moving back to avoid a strike, especially one coming straight at you is bad. You are putting your momentum into the direction your opponent is hoping to drive you into in the first place. So of coarse if he connects, you are going back and most likely down. Covering up is bad becuase you limit your range of vision and place your hands in a position where they are not immediately prepared to counter strike. Bring your hands up high to defend this attack is good, but what we see over and over is fighters totally covering themselves up which allows the attacker, even if he misses the jump punch attempt, to continue with strikes which often times can be even more successful especially if he switches and begins to attack the open body.
To demonstrate my point and to help explain what could or should be done, let's look at GSP's superman punch on Matt Hughes (UFC 65).
Matt sees it coming and not sure what to do he wildly throws his hands out in front of him and starts backing up. GSP connects to the forehead with the SM punch which clearly rocks Matt. However, it was not the SMP that knocked matt down. The SMP allowed GSP to close the distance with matt moving backward so GSP doesn't have to worry about a takedown and leaves matt open for a nice 3 punch combo by GSP which ended with a sweet short left hook which planted Matt on his butt. This is an example of the SMP working to perfection. But it only worked because Matt either panic'd or had no clue what to do. Ok, then what could have or should have Matt done? Simple, (I say simple because I am analysising this after the fact and wasn't standing there under attack) anyway, Matt should have slipped the punch to the left (Matts left, Georges right) parried the punch, and counter punched the now wide open GSP and the outcome could have been totally reversed. Allow me to break this down. Since George was attacking with his right hand, (he was lunging foreward with his right hand) Matt clearly saw it coming. while keeping his hands up, He should have stepped to his left, which of put him to the outside of George's right hand and clear of any potential followup strikes. Then (or more actually at the sametime) he parrys Georges right hand. Even the slightest slap to George's right hand at this point would have futher put George off balance and out of position. Either way at this point Matt would have been on the outside of GSP's right hand and GSP would be wide open for any assortment of counter attacks.
The Super Man Punch is a high risk move that if succesful can gain the fighter huge benefits. In MMA it has proved that even when unsucessful it seldom has much of a negative effect for the fighter and often leads to opening up other offensive opportunities. This in my opinion, as I stated before is due to poor defensive techniques. Boxing as a sport has taken the art of the punch and turned it into a sweet science. But most MMA fighters and fans give very little credit to boxing as a viable style in the MMA arena. While I tend to agree that there is alot about boxing that is counter productive or is simply bad form (I know, Ive had to over come most of them), most MMA fighters do not poccess the defensive techniques that most boxers do. (I am refereing to defense against punches). Granted, the Boxer has nothing else to worry about. His opponent is not going to kick him or go for the takedown, but I firmly believe if the average MMA fighter would concentrate more on their boxing skills we would see less of the Superman Punch or at least more of it being countered and its weaknesses being exploited. But hey, this is just my opinion and I thank you for taking the time to read it.